A Layer 2 customer network with its own physical connectivity can be connected to a provider backbone network at more than one point of attachment. This type of topology is called dual-homing and is used to increase the reliability of a data transport connection for a customer network. For example, such network topologies are designed to protect a customer network against the failure or removal of particular network components by providing redundant network paths.
The customer networks may use their own instances of spanning tree protocol (STP) to configure and partition their network's active topology so that the provider backbone connectivity does not result in a data loop. However, reconfiguration of a customer's active topology can result in the apparent movement of customer end devices from the point of view of provider backbone edge bridges. For example, in instances where a particular provider edge bridge fails, a dual-homed customer end device may send frames over the alternative redundant network path. The other provider edge bridges may however have address tables, e.g., bridging tables containing MAC (Media Access Control) addresses, which still refer to the previous active data path. Any bridged traffic destined from a remote customer end device to the dual-homed customer device may accordingly be wrongfully encapsulated with data in the address tables and sent over a MAC tunnel to the failed provider edge bridge, resulting in the data not being received by the destination customer end device and the data therefore being black-holed.